Meluadrine tartrate

This study was designed to elucidate the effects of meluadrine tartrate on maternal metabolic responses and fetal hemodynamics in unanesthetized, chronically instrumented pregnant goats. After the administration of meluadrine tartrate to pregnant goats or directly to fetuses, changes in heart rate (HR), arterial blood pressure and arterial blood pH, gasses, electrolytes and metabolic responses were measured. The constant administration of meluadrine tartrate (0.1 microg. kg(-)(1). min(-)(1)) to pregnant goats resulted in the increases of maternal HR, glucose and free fatty acid and the decrease of maternal blood K(+) concentration. The direct escalating administration of meluadrine tartrate (0.01, 0.03 and 0.1 microg. kg(-)(1). min(-)(1)) did not increase the fetal HR, while ritodrine hydrochloride (0.3, 1 and 3 microg. kg(-)(1). min(-)(1)) to fetuses increased the fetal HR dose-dependently. The present study suggests that meluadrine tartrate has a mild influence relative to the effects of ritodrine to the maternal metabolic responses and fetal cardiovascular function.

The kinetics of racemization of meluadrine tartrate in aqueous solution was investigated by HPLC, over the pH range of 1.2 to 12 at 40, 60 and 80 degrees C. The racemization was followed by measuring both the residual (R)-enantiomer and formed (S)-enantiomer of meluadrine. The pH-racemization rate profile of meluadrine showed a minimum racemization rate constant between pH 4 and 6, and the rate constant increased rapidly with decreasing pH below pH 3. In the basic region, the racemization rate constant showed a maximum at around pH 9. Four pathways of racemization of meluadrine are proposed, depending on the dissociation state of the phenolic and amino groups. The calculated racemization rate-pH profile agreed well with the observations. The values of activation energy (95-115 kJ/mol) suggest that a similar quinoid intermediate is involved throughout the pH range examined. The objective of this study is to clarify the racemization mechanism of benzylalcohol derivative with phenoric group. This study offers fundamental knowledge for the other benzylalcohol derivatives, which have similar moiety structure.